The present invention relates to an internal-gear pump, in particular for a hydraulic circuit of a motor vehicle drivetrain, having a housing which has a first fluid port and a second fluid port, having an inner rotor which is mounted in the housing so as to be rotatable about an inner rotor axis and which has an external toothing, and having an outer rotor which is rotatable in the housing about an outer rotor axis and which has an internal toothing which, to generate a pump action, engages with the external toothing of the inner rotor.
The invention also relates to a hydraulic circuit, in particular for a motor vehicle drivetrain, having an internal-gear pump of said type.
For hydraulic circuits of motor vehicle drivetrains, it is known to use hydraulic pumps in the form of gear pumps. With regard to gear pumps, a general distinction is made between external-gear pumps, internal-gear pumps and toothed-ring pumps. The expression “internal-gear pump” is in the present case intended to encompass the expression “toothed-ring pump”. In both pump types, an inner rotor and an outer rotor run eccentrically with respect to one another. In the case of a toothed-ring pump, the internal toothing generally has precisely one tooth more than the external toothing. In other internal-gear pumps, the number of teeth on the internal toothing is considerably greater than that on the external toothing, wherein the teeth are sealed off by means of a sickle-shaped structure.
Such pumps are generally known. In hydraulic circuits of motor vehicle drivetrains such pumps may be electrically driven, specifically by means of an electric motor, which drives, for example, the inner rotor. Here, the pumps are used, for example, for generating a working pressure for a hydraulic actuator arrangement. A further use is that of supplying lubricating and/or cooling oil to clutch and transmission components.
In many applications, there are numerous components to which a supply is to be provided, which components should be supplied with specific volume flow rates of oil on an operation-dependent or strategy-dependent basis. Such components can each be regarded as hydraulic consumers. For example, one hydraulic consumer may be used for lubricating and/or cooling a dual-clutch gearbox, whereas another hydraulic consumer is formed by a cooling circuit of a drive motor, which may for example be in the form of an electric machine for providing drive power for the motor vehicle.
For a volume flow of hydraulic fluid provided by a pump of said type to be distributed between two or more such hydraulic consumers, it is known to connect a pressure outlet of a pump of said type to a valve, in particular a directional valve. Said directional valve is then generally activated by means of a superordinate control unit. In implementing this variant, it is a problem that, for the electrical actuation of the valve, lines must be laid from a central controller, which is often arranged outside a transmission or clutch housing, to a region of the pump, which is generally arranged in the interior of the housing.
A further option for providing a supply to two hydraulic consumers by means of one pump consists in designing the pump to exhibit bidirectional characteristics. Depending on the direction of rotation, one of the two fluid ports of the pump is then a pressure port, and the respective other is then a suction port. Since it is generally also the case here that fluid must be delivered out of a sump, it is then necessary, by means of a complex check valve arrangement which comprises four check valves, for example, to ensure that, in each direction of rotation, fluid is drawn out of the fluid sump and discharged via the respective pressure port.